Liquid level gauge for tanks



Feb. 6, 1945. E. P. DU PONT ET AL LIQUID LEVEL GAUGE FOR TANKS Filed Nov. 1, 1943 gum;

j I j. 19 7 ?1 ATTO EYS

Patented Feb. 6, 1945 UNITED STATES PA NT 'oFFICE:

2,368,705 v LIQUID LEVEL GAUGE FOR TANKS Eleuthere Paul du Pont, Montchanin, DeL, and Y Stephen du Pont, Wilbraham, -Mass.,-' assignors- I to Indian Motocycle Company, Mass, a corporation of Massachusetts Application November 1, 1943, Serial No. 508,618"

'14 Claims.

The present invention relates to a liquid level indicating gauge for liquid enclosing tanks, and has for its object the provision of simple and efiective means for making visibly apparent the relative amount of liquid in the tank.

The present embodimentis more particularl adapted for use with gasoline tanks of motorcycles and for this purpose is mounted in the top wall of said tank in front of the rider whereby the condition of the tank as to its content of gasoline will be readily apparent at all times.

The optical laws governing the operation of the present device are well understood; For instance, the critical angl for total reflection of light at a boundary between glass and air is about 425, and said critical angle for a boundary .between glass and liquid such as water or gasoline is about 625 whereby light will be reflected from a boundary of glass and air at all angles of incidence between 42.5" and 90, but froma boundary of glass and liquid the light will not be reflected unless the angle of incidence lies between 62.5 and 90". This means that a large part of diffused light reflected fromglass in contact with air will not be reflected from glass in contact with liquid.

As a consequence, light conducteddownwardly through a glass rod terminating at its lower end in oppositely disposed obliquely inclined faces each at an angle of 45 to the vertical, will be largely reflected back upwardly in said rod when its lower end is in contact with air but will be largely refracted into the liquid and absorbed thereby when said lower end of the rod is immersed in liquid. Such a rod extended downwardly into a darkened chamber such as a closed tank of gasoline when exposed to light at its upper end, will appear relatively dark at said upper end when its lower end is immersed in the gasoline and will appear relatively bright from reflected light when its lower end is not immersed in said gasoline and in contact with air only. p

The present invention also employs the same principles of light reflection from prismatic or faceted surfaces to provide visible indicia for the upper end of the liquid level indicating rods and for directing beams of light downwardly into said rods from a. light source located laterally at the upper end of said rods. The several features of advantage and improvement over prior devices of this character will become apparent in the following more detailed description of a preferred embodiment of the invention taken in connection with the accompanying drawing in which several rods:

Springfield,

Fig. 1 'is, a side view of'the' complete gauge instrument with its mounting means partially in section and shown as mounted in the to'p wall of a gasoline tank, only-partof which appears;

Fig. 2 is a plan view of the same looking down and showing the indicia marks atthetop the Fig. 3 is an enlarged-detail view at, end of one or the indicating rods 1 Fig. 4 is a view'lookingup li e 0f I Fig. 5 is a view in section of a'slightly modifiedform of mounting means'fo'r, the-indicating rods; and i Fig. 6 is an enlarged'detail view at theiupper end of one of the rods shownin Fig. 5.1 g; Referring more particularly to the: ."drawing; the top wall of an enclosed gasolinetanksuch as currently used 011 a motorcycle'is indicated-at I. The mounting" means-of 'thefgau'ge instrument comprise a cylindrical holding block ,2=of transparent material such as glasaLucitaorthe like, a cylindricalcoverj block 3 of similar trans parent material superposed on the samfe'z allclose 1y fitted and retained together withina casing can 't d i are:

comprising a cylindrical body I and capfin'eniber for visibility.

Fastened by v 2 are a plurality of vertically-depending liquid level indicating rods 6,1,8, 9,.and III respectively. While fiVe of such rods are here prefer ably employed, a-greater'or less number may be used if desired. As shown, these rods are 'of different lengths and aremounted with their upper squared off ends flush with the upper surface of the holding block 2. The holding block and its a close fit in the; holdingblock oppositely disposed, obliquely inclined facesl I and? I2 I" each at angle -preferably 45 to the vertical; The :lower .end lot the rod I may be .of I

conicalfor pyramidalshape ofthesame 45- angle of inclination-zfor- :the same efiect;

such-as -indicated at A in dotted line passing downwardly in said rod "will 'be; completely 'ree flected atzthe surfaces "I l and I2 in the directions the lower end i of said :rod is-immersed in; liquid theray of'light A-will not be completelyrefiected at the surface 1 I butawill beaslightly refracted:

anddispersed into theiliquidfias indicated by-dotdashsline B.- Such:.rays of-light refracted into the :liquid will be-absorbedthereby and conse-;

quently the upper end. of-the'rod will appear rela tivelydark dn'contrast-with its appearanc when the -rod was free otli quid;'-,, Inthis manner i-the several rods'bya comparison or their appearance will indicate the various conditions :of *liquid in theztank.

Appropriate indicia marks areprovided forathe upper ends of --said"rods.i' These; markings :preferablyi'comprise prismatic projections" formed on t the lower side "ofthe= block-'-:3 andeeach marking being positioned within. arecess suclras-sl 3 .ofsaid cover-block: 3-which is in register with the upper endiof its respective indicat'ingrrodi As shown in Figs; 3 and 4,3 theindicia:=marking"1' which" corresponds to the upper end of rod '6 is gformed When :the vlower zendiof .suchj a rod; is. not immersed in liq-l llidx and light'shineston 1 its, upper end, a beam.

shown" and turned :backupwardlyhi said rod with theresult that this and ;.other. similarly areflected V rays willicause the-'upperend'of said rodtoap- 7 pear; relatively bright. Onwthe. other-hand; when by e-triangular faceted projection with sides l4 and" lieachiinclined at an" angle of 45 to the vertical. It will hesunderstoodythat-light shiningsdown through the :cover block3as indicated bylthe ray. at the dotted line-zcy Fig. 3, willibe totally reflected back upwardlyiby: said surfaces l4 and I5 so as to make the indicia; a

thereof clearly=visible. Thus when-th'e:tanlris full the lower end "ofrsrod :6 for' instance will: be I immersed-in liquidandathexupper end of'said" rod will' appear relatively dark. Withinthis dark" area of rod however; will ap ar in .bright: visible form the indicia marking l, because of;

thelight'refieoted back upwardly from the faces I4 andl l 5. When the rod 6' 'is uncovered by'liq':

7 uid its whole top .end will appear bright and the 7 indiciamarking 1 will not'sho'w 'upby suchstrong contrast.

Ini order'that the cover block. 3i may furnish aibrigh't backgroundfor the indicia marks and lupperends or the indicating .rods,-the-lower surface'=t-o'f-'theholdingfblock 2 .is formed with ax ribbed faceted surface l6" which will reflect light upwardly from :the bottom* of said holding? block l; v In -Fig.2 5I have :shown'; provision for illuminating -the'top ends of the-several indicating rods by an artificial source of". light :such as bulb ll wedge-shaped cut 22, the side% of which isslopedrat tothe vertical. Thus a ray of lightsuch as D coming laterally into said recess 13;

will be deflected downwardlyby the faceted surface 23'into the rod 8'- for illuminating the same.

Such artificial means of illumination are desirable for use. of the instrument at night when sunlight is absent.

We claim; v 1. An'indicating level'gauge for liquid enclos- 'ingrtanks comprising in combination, mounting means in the top wall of saidtank,-a plurality of rodsof transparent material depending vertically from said mounting means having lower ends terminating at'differentlevels in said tanksthe lower endofeach rod being formed with oppositely disposed obliquelyinclined surfaces at an .angleof inclination so related to the refractive indexof saidrod-material as-to totally reflect upwardly light passing downwardly in said rods when the lower ends are uncovered by liquid; and'to-transmiit refracted light into liquid when saidlower'ends are covered by liquid, and distinguishable'indicia marks associated with the upper ends ofrsaidrods, each indicia mark'for for said blocks mounted in an opening in the .top 'wall ofsaid tank, a plurality of rods of transparent material depending vertically from;

said holding block with their lower ends at dif-' ferent levels in said tank, the lower end of each rod being formed with oppositely disposed obliquely inclined surfaces at an angle of inclinationapproximately 45 to the vertical so as to totally reflect upwardly the light passing down-v wardly'in said rods when thelower ends are uncovered by liquid and to transmit refracted light-into liquid when said lower ends are covered by liquid, distinguishable indicia marks associated with the upper endscf said rods, each indicia, markior its. respective 'rod formed by relatively small prismatic surfaces positioned in V conjunction-with the upper end of said rod and arranged to reflect light upwardly therefrom;

3. An indicating level gauge for liquid enclosing-tanks comprising iii-combination, a rod holding :block having superposed thereon a cover "block'of transparent material and a retaining casing for said blocks mounted in an opening in the top wall ,of said tank, a plurality of rods p t on d laterally of; then-upper -ends'- of said 7 rods. of fthe invention is slightly' modified from that previously 'described'sand comprises "a body por- 1 tion IB -an'd a-hinge cover portion l 9 formed with a housing recess at one side; for said. bulb socket r 2 I e indicates a leadiin wire connection for-3 20: said bulb; In this modification. also faceted meansare provided for directing; raysoff-light from r the '='bulb I 1* downwardly" intothe several rods. Referringzto Fig: 6;"the 'cover blocks hasirin its recessed portion I 3' a circumferential The casing forrtheq-blocks inthis form? of transparent material fixed in said holding block and depending vertically therefrom with their. upper ends substantially-flush with the upper surface of said holding block and with their lowerends at difierentzlevels in said tank, thevlower end'of each rod being formed with oppositely disposed obliquely inclined surfaces at an angle of inclination approximately 45 to the vertical-so as to totally reflect upwardly the light passing downwardly in said rods when the lower end'siare uncovered by liquid, and to transmit refracted light into liquid when said lower ends are covered by liquid, distinguishable indiciamarks associated'with the upper ends of said rods, each indicia mark'for its respective rod comprising relatively small prismatic surfaces formed in a recess on the underside of said cover zblock, positioned in conjunction with the upper ing tanks comprising in combination, mounting means in the top wall of said tank, a plurality of rods of transparent material depending vertically from said mounting means having lower ends terminating at different levels in said tank, the lowerend of each rod being formed with oppositely disposed obliquely inclined surfaces at an angle of inclination approximately 45to the vertical so as to totally reflect upwardly light passing downwardly in said rods when the lower ends are uncoveredby liquid, and to transmit refracted light into liquid-when said lower ends are covered by liquid, an electric bulb positioned at one side of said mounting means and arranged to shine light laterally across thegupper ends of said rods, and prismatic light reflecting surfaces arranged in said mounting means to reflectlight from said bulb downwardly in said rods.

5. An indicating level gauge for liquid enclosing tanks comprising in combination, a rod holding block of transparent material having superposed thereon a cover block of transparent material, said holding block having a lower horizontally disposed surface ridged throughout its area with relatively small prismatic surfaces arranged at an angle to reflect light upwardly through said block, and a retaining casing for said blocks mounted in an opening in the top wall of said tank, a plurality of rods of transparent material depending vertically from said holding block with their lower ends terminating at different levels in said tank, the lower end of each rod being formed with oppositely disposed obliquely inclined surfaces at an angled inclination approximately 45 to the vertical so as to totally reflect upwardly light passing downwardly in said rods when -the lower ends are uncovered by liquid, and to transmit refracted light into liquid when said lower ends are covered by liquid.

6. An indicating level gauge for liquid enclosing tanks comprising in combination, a rod holding block of transparent material having superposed thereon a cover block of transparent material, said holding block having a lower honzontally disposed surface ridged throughout its area with relatively small prismatic surfaces arranged at an angle to reflect light upwardly through said block, and a retaining casing for said blocks mounted in an opening in the top wall of said tank, a plurality of rods of transparent material depending vertically from said holding block with their lower ends at different levels in said tank, the lower end of each rod being formed with oppositely disposed obliquely inclined surfaces at an angle of inclination approximately 45 to the vertical so as to totally reflect upwardly light passing downwardly in said rods when the lower ends are uncovered by liquid, and to transmit refracted light into liquid when said lower ends are covered by liquid, distinguishable indicia marks associated with the upper ends of said rods, each indicia mark for its respective rod formed by relatively small prismatic surfaces posftioned in conjunction with the upper ends of said rod and arranged to reflect light upwardly therefrom.

7. An indicating level gauge for liquid enclosing tanks comprising in combination, a rod holding block of transparent material having superposed thereon a cover block of transparent materiall said holding block having a lower horizontally disposed surface ridged throughout its area with relatively smallprismatic surfaces arranged at an angle to reflect light upwardly through said block,. and a retaining casing for said blocks mounted in anopening in the top wall of said tank, a plurality of rods of transparent material depending vertically fromrsaid holding block with their lower ends at different levels in said tank, the lower end of each rod being formed with oppositely disposed obliquely inclined surfaces at an angle of inclination approximately 45 to the vertical so as to totally reflect'upwardly the light passing downwardly in said rods when the lower ends are uncovered by liquid, and "to transmit refracted light into liquid when said lower ends are covered by liquid, distinguishable indicia marks associated with the upper ends of said rods, each indicia mark for its respective rod comprising relatively small. prismatic surfaces formed ina recess on the underside'of'said cover block, positioned in conjunction with*the upper end of said rod and arranged to 'refiect'light upwardly therefrom. a a

8. An indicating level gauge for liquid enclosing tanks comprising in combination, mounting means in the top wall of said tank; a plurality. of

rods of transparent material depending'ver'tically from saidF-mountin means having lower ends terminating atdifler'ent levels in said tanks, the lower end of each rod being formed with oppositely disposed obliquely inclined surfaces at :an'

angle of inclination so related to the refractive index of said rod material as to totallyrefiect upwardly light passing downwardly in said rods when the lower ends are uncovered by liquid, and

to transmit refracted lightvinto liquid wherrsaid lower ends are covered by liquid, and the upper ends of said rods each having associated therewith an individual indicia number formed by prismatic surfaces which reflect light upwardly;

9. An indicating level gauge for liquid enclosing tanks comprising in combination, a rod holding block having superposed thereon a cover block of-transparent material and a retaining casing for said blocks mounted in an opening in the top wall of said tank, a plurality of rods Oftransparent material depending vertically from said holding block with their lower ends at different levels in said tank, the lower end of each rod block of transparent material and a retaining casing for said blocks mounted in an opening in the top wall of said tank, a plurality of rods of transparent material fixed in said holding block and depending vertically therefrom with their upper ends substantially flush with the upper surface of said holding block and with their lower ends at different levels in said tank, the lower end of each rod being formed to totally reflect upwardly the light passing downwardly in said rods when the lower ends are uncovered'by liquid, and to transmit refracted light into liquid when said lower ends are covered by liquid, distinguishable indicia marks associated with the upper ends of said rods, each indicia mark for v its respective prod comprising relatively small underside of said cover block, positioned in conjunction .with the upper end of said rod and arranged to reflect light upwardly therefrom., 1

11. An indicating level gauge for liquid enclosing tanks comprising in combination, mounting means in the top wall of said tank, a plurality of rods of transparent material depending vertically from said mounting meanshaving lower ends terminating at difierent levels in said tank,

the lower end of each rod being formed to totally posed thereon a cover block of transparent materiaL. said holding-block having ,a lower hori-L zontally disposed surface ridged throughout its.

area with relatively-small prismatic surfaces arranged at an angle to reflect light upwardly through said block, and a retaining casin for saidblocks mounted in an opening in the top wall of said tank, a plurality of rods of transparent material-depending vertically from said holding block with their lower ends terminating at difierent levels in said tank, the lower end of each rod being formed to totally reflect upwardly light passing downwardly in said rods when the.

lower ends are'uncovered by liquid, and to transmit refracted light into liquid when said lower. ends are covered by liquid.

13. 'An indicating level gauge for liquidenclos- 'ing tanks comprising in combinatiom'a'rod holding block oftransparent material having superposed thereon a cover block of transparent ma- I terial, said holding block having a lower horizonprismatic surfaces formed in a recess on the,

tally disposed surface ridged throughout its area with relatively small prismatic surfaces'arranged at an angle to reflect light upwardlyjthrough said block, and a retaining casing for said blocks -mounted in an opening in the top wall of'sai'd tank, a plurality of rods of transparent mate rial depending vertically from said holding block with their lower ends at different levels in said tank, the lower end of each rod being formed to totally reflect upwardly light passing downwardly in said rods when the lower ends are uncovered by liquid,

and to transmit refracted light into lliquid when said lower ends are covered by liquid, distinguishable indicia marks associated with v, the upper ends .of said rods, each indicia markfor its respective rod formed by, relatively small prismatic surfaces positioned in conjunction with the upper ends of said rod and arranged to reflect light upwardly therefrom. Y v

l4. An indicating level gau e for liquid enclosing tanks comprising in combination, a rodv holding block of transparent material having superposed thereon a cover block of transparent materiaLsaid holding block having a lower horizontally disposed surface ridged throughout its areawith relatively small prismatic surfaces arranged. at an angle to reflect light upwardly through said block, and a retainingcasing for said blocks mounted in an opening in the top wall of said tank, aplurality of rods of transparent material depending vertically from said holding block with their lower ends at different levels in said tank, the lower end of each rod being formed to totally reflect upwardly the light passing downwardly in said rods when the lower ends are uncovered by liquid, and to transmit refracted light into. liquid when said lower ends are covered by liquid, distinguishable indicia marks associated with, the upper ends of said rods, each indicia mark for its res e tive .rod comprising relatively small prismatic surfaces formed in a recess on the underside of said cover block, positioned in conjunction with the upper end of said rod and arrangedto reflect light upwardly therefrom. A

ELEUTHERE PAUL DU PONT. STEPHEN DU PONT. 

